The studies to be conducted under this contract will evaluate the toxicity and carcinogenicity of butylbenzyl phthalate administered in the diet for two years to male and female F344 rats and B6C3F1 mice. In addition, these studies will evaluate the effect of reduced weight gain on tumor incidence in rats. This will be accomplished by feeding special groups of rats an amount of feed which will maintain their body weights below that of the ad lib fed animals. All moribund animals, as well as those that survive to the end of the study, will receive a complete gross examination. All grossly visible lesions and all tissues containing non-neoplastic or neoplastic lesions associated with chemical exposures will receive a complete histopathologic examination.